There is need to reduce time and liability while improving efficiency in eliminating leaks in fluent material distribution systems, particularly, termination of a blowing gas leak in gas distribution systems. At the present time, approximately four hours is involved in rendering a gas main safe. A broken underground main currently requires on site men and equipment to dig separate holes on both sides of the break to the main. After the broken section of the pipe has been located, separate holes on both sides of the break are dug and the squeezing machines are applied at the two points dug and then the leaking section of pipe is repaired either by replacement with a new section and/or other type of repair.
In the prior art, U.S. Pat. No. 4,257,466 discloses a system incorporating the use of valve boxes which can receive a pipe squeeze apparatus. However, in this patent, the squeeze apparatus required that the valve box be large enough to accomodate the fitting of a component underneath the plastic pipe very much in the way of conventional plastic pipe squeeze devices. In this prior art device, the valve box is designed to permit the squeeze apparatus to slide to one side of the pipe and then is guided there by means of the bottom or camming of the device. According to the present invention a relatively narrow cylindrical valve box arrangement is provided in which the valve box has telescoping portions to adjust for different heights between surface elevations of the pipe and the ground level. According to the invention, a broken gas main, for example, can be rendered safe in a very short period of time (within seconds) without the use of a backhoe and/or pavement breakers. The judicious location of the valve boxes according to the invention permits isolating certain sections of the line between squeeze points without affecting service to the majority of the customer's on the line. Since gas companies are governed by the Department of Transportation (they transport gas over state lines between various points by the use of pipe line, they are subject to Department of Transportation (DOT)) regulations and these regulations require that any plastic main inside of a vault (which is any opening from ground surface to the main that is larger than 8 inches) must be shielded with steel pipe. Hence, the term "valve box" is intended to refer to any opening (cylindrical, rectangular, hexagonal etc.) in section from the ground surface to the main that is 8 inches or smaller and which does not thereby require steel shielding which would prevent squeezing of the plastic pipe. Thus, instead of using conventional valves and valve boxes, all that is present in the valve box is the passing portion of the plastic pipe. Thus, instead of a valve in a valve box or vault, (which requires periodic maintenance and record keeping in addition to turning-off of the valve to insure its operability) applicant's invention permits liberal placement of the squeeze-off points where they avoid the expense of a valve which requires much specialized equipment and work (i.e. plastic fusing equipment, specially trained personnel, costly valves and extensive backfilling and paving).
The squeeze device according to the present invention reaches into a valve box with a 6 inch inside diameter and approximately four feet (but which can vary and any such variation can be easily accomodated by the telescoping valve box of this invention) of depth in order to squeeze-off a plastic main which is up to 23/8 inch in outside diameter exerting a minimum pressure of 800 pounds per square inch. The squeeze machine of this invention is activated with a rachet that drives a left and right hand threaded bar at the upper end of the machine above the ground level which, in turn, operates two levers in opposite rotational directions. This opposite rotary action is transmitted by a 11/2 inch pipe rotating inside of a 2 inch pipe which is journaled for supporting the smaller pipe for rotation. Thus, the two pipes are rotated about a common axis and this transmits the squeezing force to squeeze bars which are secured to the lower ends of the two pipes and at a same radial distance from the axis of rotation. This permits the maximum spacing between the device to be not much greater than the 23/8 inch outside diameter of the pipe to be squeezed-off plus the dimensions of twice the radius that the squeeze bars are radially spaced from the axis of rotation. The squeeze bars must remain parallel to each other while exerting pressure on the pipe and, the spacing of the squeeze bars (their closest distance together) must be closely controlled in order to prevent damage by over squeezing of the pipe. Hence, a stop member is provided to limit the minimum distance between the squeeze bars. As the pipe is squeezed it becomes tall and thin in a vertically oriented direction. According to the invention, a spacer is offset from the squeezing bars and this spacer positions and rests the device on the plastic main away from the squeeze point to allow the plastic to spread as it is squeezed preventing the squeeze portion of the pipe from hitting the top of the device. Moreover, the extended vertical and parallel squeezing device permits a reduction in expense and improves reliability because it is relatively maintenance free, does not require special records and/or special installation or personnel.
There is no interruption of gas flow during valve box installation (the lower edge of the valve box has a pair of aligned slots which fit over the plastic pipe) and there is no costly valve. Finally, and most important, the ability to use any point of the plastic pipe in conjunction with a valve box as a potential valve in emergencies is an important adjunct of the invention.
While I have referred to valve box and squeeze device in Ray U.S. Pat. No. 4,257,446 as part of the prior art, reference is also made to the squeeze pipe shut-off valves manufactured by the DuPont Company, squeeze type assemblies as manufactured by the PNS Engineering Division the Rigid Tool Company subsidiary of Emerson Electric Company, Gill U.S. Pat. No. 3,589,668 and Dresden U.S. Pat. No. 3,102,710, Press U.S. Pat. No. 3,733,046, Rink U.S. Pat. No. 3,770,023, Melsheimer U.S. Pat. No. 3,774,876, Press U.S. Pat. No. 3,791,617 and Press U.S. Pat. No. 3,811,649.